Twelve numbers explain most of what a battery can and cannot do on a Welwyn Garden City roof. They are PVGIS’s monthly estimates for a 4 kWp array facing due south in the town, and they run from about 136 kWh in December to about 483 kWh in July. A battery does not change those numbers. It only moves electricity from the hours the roof makes it to the hours the house needs it, and how much there is to move depends on the month.
This guide reads the year month by month and turns it into a sizing argument. For where a battery goes in a Garden City terrace, Estate Management consent and the UK Power Networks paperwork, see our page on battery storage in Welwyn Garden City.
Twelve months from one Garden City roof
We ran the European Commission’s PVGIS 5.3 tool at the Welwyn Garden City town-centre point our battery page uses, with the site’s standard settings: 4 kWp, 35° tilt, due south, 14% system losses, building-mounted. The monthly estimates, rounded:
- January 154 kWh, February 209, March 341, April 441
- May 471, June 479, July 483, August 438
- September 375, October 267, November 183, December 136
For a Welwyn Garden City roof, that is about 16.0 kWh a day in June and about 4.4 kWh a day in December, on PVGIS’s own daily averages. December is about 28.4% of June on our arithmetic. These are estimates for an unshaded south-facing roof, not a survey result or a promise of what any system will produce.
The Met Office’s long-term averages for Welwyn Garden City use its Rothamsted station in Hertfordshire, which tells the same story in hours: about 209 hours of sunshine in July against about 56 in December, over 1991–2020.
June: more than the house uses
Ofgem’s typical domestic consumption value, from 1 July 2026, is 2,500 kWh a year for a medium, single-rate household. On our arithmetic that is about 6.8 kWh a day, although real use is not flat across the year. In June, a south-facing 4 kWp roof in Welwyn Garden City makes about 16.0 kWh a day, more than twice that average. A battery in June has plenty to store; the question is how much of it the evening actually needs before the surplus is exported anyway.
December: less than the house uses
In December the same roof makes about 4.4 kWh a day, less than the average household’s daily use before any of it reaches a battery. Most of it is used as it is made, in the middle of the day, and a battery may see very little. That is why its winter value in a Welwyn Garden City home comes mostly from the tariff: where a tariff has a cheaper overnight rate, the battery can charge from that and run the house through the evening. Our guide to whether solar panels work on cloudy days covers why output falls so far without stopping.
The shoulder months decide more than the extremes
On a Garden City roof, March and October are where sizing shows. On our arithmetic, March’s 341 kWh is about 11.0 kWh a day and October’s 267 kWh about 8.6 kWh a day, both above the 6.8 kWh average but not by much once daytime use is taken out. November, at 183 kWh, is about 6.1 kWh a day. A battery that is well used from March to October and quiet from November to February is doing its job; one sized for June’s surplus will sit part-empty for half the year.
What the Estate Management Scheme changes
Most homes in Sherrards and Handside wards, and parts of Haldens, Peartree, Hollybush and Howlands, sit inside the Estate Management Scheme, which Welwyn Hatfield Borough Council runs separately from planning. Its published approach favours panels on a rear or side roof slope, allows a principal slope only where the case officer judges the street scene would not suffer, and does not accept wall-mounted panels in any position; a detached garage or outbuilding may be more acceptable. On the town’s terraces, home to 37.4% of households in its built-up area at the 2021 Census, the slope that gets consent may face east or west, or hold fewer than 4 kWp, and either generates less than the figures above. A smaller array lowers every month in proportion, and the battery should follow it down.
Size to the evening, not the season
The Energy Saving Trust says a typical home system might be 10 kWh, and that there is no exact formula for working out what you need. For a Welwyn Garden City household, the useful number in practice is your evening use: what the house draws between the panels fading and a cheaper rate starting, if your tariff has one. Twelve months of smart-meter readings show it better than any average. Our guide to what size home battery you need sets out the method step by step.
Seasons and power cuts
One seasonal point is often missed. A standard grid-tied battery shuts down with the grid, so it keeps nothing running in a power cut unless backup was designed in. Even with backup, a winter cut in Welwyn Garden City is covered mainly by whatever the battery held beforehand, because December’s roof adds so little. Inside the Estate Management Scheme, any backup switching is best kept indoors with the battery.
For the roof side, including Estate Management consent and the conservation areas, see our solar panels in Welwyn Garden City page, and for neighbouring towns our solar panels in Hertfordshire hub. If the numbers for your roof do not support a battery, the survey should say so.
Sources: European Commission JRC, PVGIS 5.3 PVcalc (PVGIS-SARAH3 2005–2023; 4 kWp, 35°, due south, 14% losses, building-mounted; town-centre point 51.8015, -0.2045, run October 2026); Met Office, location-specific long-term averages, Rothamsted, 1991–2020; Ofgem, Typical Domestic Consumption Values (from 1 July 2026); Energy Saving Trust, Battery storage (updated 19 August 2026); Welwyn Hatfield Borough Council, Estate Management Scheme; WGC EMS, Current Estate Management Policies and Design Guide: Photovoltaic Cells and Solar Hot Water Panels; ONS, Towns and cities, characteristics of built-up areas, Census 2021 (Table 5c).